Ocular examinations are widely performed for the purpose of preemptive medical care for lifestyle-related diseases and other diseases occupying major causes of blindness. A scanning laser ophthalmoscope (SLO; hereinafter referred to as an SLO imaging apparatus), an ophthalmology apparatus based on the principle of a confocal laser scanning microscope, performs raster scan on a fundus with a laser beam (i.e., a measuring beam) and, based on the light intensity of a relevant return beam, quickly acquires a high-resolution retinal image.
In recent years, an adaptive optics (AO)-SLO imaging apparatus including an adaptive optics (AO) has been developed. The AO measures an aberration of the subject's eye in real time by a wavefront sensor and corrects the aberration of the measurement beam and its return beam occurring at the subject's eye by a wavefront compensation device. The thus-configured AO-SLO imaging apparatus can acquire a high lateral resolution image and accordingly detect retinal capillaries and visual cells.
As a method for comparatively displaying measurement results regarding blood vessels based on an ocular SLO image, a non-patent literature 1 (Johnny Tam, Joy A. Martin, and Austin Roorda, “Noninvasive visualization and analysis of parafoveal capillaries in humans”, Investigative Ophthalmology and Visual Science, Vol. 51 No. 3, pp. 1691-1698, March 2010) discusses a technique for dividing a peripheral area of fovea centralis into four (top, bottom, left, and right) division areas centering on the fovea centralis with respect to a capillary extraction result and displaying the distribution density of capillaries in each division area (acquired by dividing the total length of blood vessels by the area for each division area).
Non-patent literature 2 (Johnny Tam and Austin Roorda, “Enhanced Detection of Cell Paths in Spatiotemporal Plots for Noninvasive Microscopy of the Human Retina”, Proceedings of 2010 IEEE International Symposium on Biomedical Imaging, pp. 584-587, April 2010) discusses a technique for recognizing a blood cells' moving range as a blood vessel area based on an SLO image focused in the vicinity of visual cells of the healthy eye, and measuring the blood cells' moving velocity and other blood flow dynamic states.
However, blood vessels seem to exist at the same position when viewed from the anterior eye, they may exist at different positions in the depth direction (hereinafter referred to as depth positions). Therefore, the blood flow state cannot be correctly grasped simply by dividing the SLO image into partial areas and displaying them.
Another issue is that, since the blood vessel diameter varies from position to position, the blood flow state cannot be correctly recognized simply by dividing the SLO image into partial areas and displaying information about the blood flow.